ES2381822T5 - Chip card - Google Patents

Abstract

The method involves transmitting a signal from a transponder unit (1) to a reader (100), in one operating mode. The reader evaluates the signal as a modulation of its own field (110) by a transponder. The unit sends the signals as load modulation or as a modulated infrared radiation. The reader operates within and outside the communication range of the transponder unit, in the respective operating modes. Independent claims are also included for the following: (A) a value document such as cheque and backnote comprising a transponder unit (B) a mobile data carrier such as chip card comprising a transponder unit (C) a mobile end device such as mobile radio unit or mobile verification terminal comprising a transponder unit (D) a system for data communication from a transponder unit (E) an interface unit for signal modulation.

Description

DESCRIPTION

Chip card

The present invention relates to a chip card with a transponder unit.

Transponders are used, for example, in RFID systems ("Radio-Frequency-Identification"). Traditionally, both the power supply of an RFID system and the exchange of data between the transponder and a reader device are carried out using magnetic or electromagnetic fields. RFID transponders have an electronic circuit and, depending on the frequency range, an antenna coil (eg 13.56 MHz) or an electromagnetic antenna (eg 868 MHz). By means of the antenna, the energy necessary for the operation of the transponder can be extracted from the field of the reader, as well as the transmission of data.

Up to a certain distance between the reader device and the transponder, also called the energy range, the transponder can extract from the field of the reader device an amount of energy that is still sufficient for the autonomous operation of its circuit. Typical power ranges for such systems are approximately 10 cm for ISO 14443 and up to 1 meter for ISO 15693 compliant systems.

The range of action within which a communication in the system by data transmission is possible can be increased by using active transponders, ie transponders with their own power supply. The power supply of an active transponder, for example in the form of a battery, operates the electronic circuit of the transponder. In turn, transponders without their own power supply are called passive transponders.

RFID systems, for example for different types of coupling, as well as load modulation using an auxiliary carrier in inductive coupling RFID systems, are described in particular in Section 3.2 of the "RFID-Handbuch" ("RFID Manual" ) by Klaus Finkenzeller.

For simple and fast wireless communication between two devices, Philips and Sony companies have developed an inductive transmission technology, known as NFC ("Near Field Communication"). This technology is incorporated, for example, in mobile phones or PDAs, to enable communication between devices or with a computer. The coupling of the two devices is made by means of coils and the carrier frequency, as in RFID systems, is 13.56 MHz. As described in more detail in the NFC ECMA 340 standard, in NFC systems there is a mode of active communication and a passive communication mode. In active communication mode, two NFC units alternately generate their own RF field as signal carriers, that is, adjusted to each other, as in a traditional mobile phone system, they switch back and forth between broadcast operation and the reception. On the other hand, in passive mode, the two NFC units must agree on which of the units acts as a reader and generates a field that can then influence the other unit by modulation of charge. Mainly due to the small antenna diameters used, with NFC systems, especially in passive mode, only short communication distances of up to 20 cm are possible.

EP 1280099 Al relates to a circuit with card and card reader function. Depending on the state of charge of a battery, the battery or a rectifier is chosen as the power source of the circuit.

DE 19800565 Al shows a traditional system consisting of a transponder and a base station in which a modified charge modulation method is used for wireless data exchange. Document US2003 / 0169152 describes a reader apparatus that can be presented as a charge modulation unit, or as a reader apparatus, without requiring a charge modulator.

Even in active transponders there is a problem that the data transmission from the transponder to the reader device is limited by the signals, which are increasingly weaker as the distance between the reader device and the transponder increases. For example, in inductive coupling systems that transmit data to the reader according to the principle of load modulation, it is generally not possible to obtain ranges greater than 1 to 2 meters, even with active transponders. On the other hand, in RFID systems that work according to the principle of backscatter ("Backscatter"), communication distances of 10 meters are usually achieved.

Therefore, the object of the invention, compared to conventional systems with active or passive transponders, is to increase the range of data transmission in a system comprising a reader / transponder apparatus and a transponder unit.

This objective is achieved by the features of the independent claim. In the claims depending on them, advantageous configurations and improvements of the invention are set forth.

The chip card according to the invention with a transponder unit for transmitting data to a reader device, to which transponder data can be transmitted by modulation of a field of the reader device, has: means for sending a signal, which is evaluable by the reader apparatus as a modulation by means of a transponder, to transmit the data in a first mode of operation to the reader apparatus, by an oscillator to generate an oscillator signal and because the oscillator is coupled by means of a PLL circuit ("Phase-Locked- Loop ”,“ phase locked loop ”) to the signal captured by the reader, which serves as a reference signal for the oscillator, and a modulator that is configured to modulate the oscillator signal by means of the data to be sent and to generate a from there the output signal.

In particular, a transponder unit emits a signal for a reader / transponder apparatus, which, by modulating its own field, can communicate with the transponders by means of a transponder, so that a conventional transponder can recognize the signal as a modulation . Instead of carrying out a charge or backscatter modulation of the field of a reader apparatus, the transponder unit itself emits a field which, for the reader apparatus, simulates a modulation of the field of the reader apparatus made by a transponder. A transponder unit according to the invention comprises means for emitting the suitably modulated signal. As a consequence, the total range of the system is no longer limited by the communication range of the reading apparatus, but is extended to the transmitting range of the transponder unit.

In order to avoid a quartz oscillator, which presents large dimensions, in an improved configuration of the invention, the oscillator is coupled with a fixed phase by means of a PLL circuit to the signal captured by the reading apparatus, when the transponder unit is in reception mode. In the transmission mode of the transponder unit, that is, during the transmission of data from the transponder unit to the reader, the regulating voltage of the PLL circuit is kept constant, so that the frequency of the oscillator is kept as low as possible. stable possible. The PLL can also be called tracking sync. The oscillator is controlled so that it follows a reference signal, in this case the synchronization signal of the reading device, with phase synchronization. The control circuit continuously compares the phases of the two signals and, in the event of an error signal, equalizes the phase of the oscillator. A PLL circuit is used primarily to stabilize or synchronize the frequency of the oscillator. Additionally, provision can also be made to bring the signal generated by the oscillator to the control module and use it as a relevant clock signal for synchronization.

In an advantageous configuration, the RFID transponder unit has its own power supply, at least one antenna for transmitting signals from and / or to a reading device, as well as an electronic circuit. The electronic circuit of the transponder unit, according to the invention, comprises an emitter consisting of an oscillator and a modulator.

In a first alternative, the modulator comprises a ring modulator. The oscillator is coupled to the battery and is provided to supply an oscillator signal to the ring modulator. Furthermore, the data signal that is generated in a control module of the transponder unit or that is supplied from the outside to the transponder unit, is supplied to the ring modulator through a second input. The data signal can be modulated with a subcarrier before being supplied to the ring modulator. It is characteristic of the ring modulator that it performs DSB modulation ("Double-Side-Band-Modulation") and that it can be used regardless of the shape of the data signal (analog or digital).

The ring modulator can be configured as an analog or digital ring modulator. In one embodiment as a digital ring modulator, an XOR logic link is preferably implemented between a carrier frequency signal and a subcarrier modulated signal. It is especially advantageous to bring a carrier frequency signal linked to the data signal via an AND gate to the digital ring modulator.

In a second alternative, the modulator performs a logical AND link of a carrier frequency signal with a modulated subcarrier signal. This modulator for the logical link of two signals is preferably used only when the data signal is a binary signal ("2-ASK", "BPSK"). In that case, the ring modulator in the transponder unit can be dispensed with. It is only necessary to use an analog ring modulator in the case of multilevel modulation (e.g. 4-ASK, 16-ASK, 4-PSK, 16-ASK, etc.) or for analog signals, in order to increase the scope of data transmission compared to traditional systems. The advantage of a modulator for the logical AND link of two signals is that it is easier to implement than an analog ring modulator.

The two modulators (ring modulator and ASK modulator) modulate the oscillator signal by means of the data signal (modulated) and supply an output signal which is then transmitted to the reader via the receiving antenna or a separate transmitting antenna.

In a preferred configuration, the modulator comprises a carrier frequency modulator, for example in the form of a ring modulator or ASK modulator, and a subcarrier modulator.

A special advantage of using the modulators described is their compatibility with the state of the art, since they supply the reader with an output signal whose spectrum (of frequencies and amplitudes) is very similar to that of a final or backscatter modulation, such as as already described. Therefore, it is not necessary to make technical modifications to traditional reading devices. Thus, the transponder according to the invention can also be operated with commercially available RFID readers, with a communication range several times greater than that of passive and also active transponders. For example, a commercially available ISO 14443 reader device, which according to the state of the art can communicate with an inductively coupled wireless chip card at a distance of approximately 10 cm, will be able to communicate at a distance several times greater with a unit. transponder, according to the invention.

An additional advantage is the compatibility with other passive and active transponders, so that the two can be simultaneously in the range of the reader and operate without influencing each other.

The transponder unit, according to the invention, only sends the data in side bands, with separation of the frequency of the data signal (modulated) with respect to the emission frequency of the reading device.

The electronic circuit of the transponder unit further comprises, in the usual way, a receiver configured in such a way that it can detect the signals of a reading apparatus. The receiver extracts the data from these signals by means of a demodulator circuit, so that at the receiver output, as a baseband signal (e.g., as NRZ code, Miller code, etc.), a stream of data transmitted by the reading device. For example, the data can be a simple instruction to activate the control module. However, you can also think of data that contains more complex instructions for the control module. The demodulated data is sent to the electronic circuit control module. A data signal is then generated in the control module, so that the data signal can also be based on the extracted data.

In a further development of the invention, the transponder unit, according to the invention, in addition to the above-described circuit comprising a receiver, a control module, an oscillator and a modulator, has a charge modulator according to the state of the art.

The voltage induced in the antenna of the transponder unit can represent a problem for the mode of operation of the modulator circuits, according to the invention, when the distance between the transponder unit and the reader device is small and, consequently, the voltage induced is high. For this reason, the data to be sent to the reading apparatus, generated in the control module, is taken, as a choice, to the load modulator or to the circuit device with modulator, according to the invention. Preferably, the switching between the charge modulator and the circuit device is performed automatically, depending on the magnitude of the induced voltage in the antenna. The switching is carried out in such a way that, within the normal range of communication, the load modulator is used, and, outside the normal range of communication, the modulator is used, according to the invention. In one configuration, when a subcarrier signal is used in the data transmission from the transponder unit to the reader apparatus, as already mentioned, a circuit device is provided to generate and modulate said subcarrier signal. In a first alternative, the circuit device is a component of the transponder unit. Another alternative in which the circuit device is not a component of the transponder unit will be discussed in detail later. Preferably, the frequency of the subcarrier signal is generated by dividing the oscillator frequency. The amplitude of the subcarrier signal is switched in the circuit device between two states, by means of the data to be sent, which is present, for example, in the form of a binary code signal. This process is called amplitude shift keying ("ASK") or ASK modulation. From a mathematical point of view, modulation to Sk is the result of multiplying the binary code signal by the subcarrier signal. The modulated subcarrier signal is then taken to the ring modulator or to the modulator for the logical link of two signals. It is also possible to carry out phase modulation, for example BPSK modulation of the subcarrier signal.

Furthermore, the transponder unit may have a voltage limiter, intended to limit the voltage induced in the antenna by the reader apparatus. In this way, among other things, the above-described problem of overloading can be avoided when the transponder unit and the reading apparatus are at a short distance from each other. For example, a shunt regulator can be used as a voltage limiter.

In particular, for communication according to ISO 14443 Type A it is important to maintain exact timing. In traditional passive transponders, synchronization is also achieved in broadcast operation (load modulation) by means of the clock signal (13.56 MHz) that the reader device receives continuously. However, in the transmission operation of a circuit device according to the invention, such a signal is no longer available. Therefore, in one embodiment of the invention an oscillator is included, for example in the form of a quartz oscillator.

The possibility of being able to read the transponder unit according to the invention at distances is not always desirable. very large, for example, to protect the private sphere. Therefore, in one configuration it is envisaged to be able to manually activate the circuit device, in case long-range communication is explicitly desired. Otherwise, communication can be done via a charge modulator located in the transponder unit, usable only for short distances. In the event that there is no charge modulator in the transponder unit, it can be provided, for example, that the transponder unit is only activated to send data when the signal emitted by the reading device contains a predetermined code.

The transponder unit can also be a component part of a mobile device, for example a mobile phone. The transponder unit can have its own antenna or it can use the antenna of the end device on which it is mounted.

According to a first alternative, the circuit arrangement for the generation and modulation of the auxiliary carrier signal is a separate component part of the final apparatus. The transponder unit then has a signal input to receive the auxiliary carrier signal from the circuit device modulated by the data to be sent. The signal input is connected via a suitable interface, in particular via a chip, for example a smart chip card, which generates and modulates the auxiliary carrier signal. According to a second alternative, the circuit arrangement for the generation and modulation of the auxiliary carrier signal is the transponder unit itself. In order to connect the transponder unit with a chip (smart card) of the end device, which prepares, for example, the data to be sent, an interface can be provided by means of which data is transmitted in binary form.

The advantage of this alternative is that the smart card chip does not need to have any type of H ^f (or RFID) interface, since all the functions necessary for data transmission are performed by the transponder unit.

Preferably, the transponder unit is integrated into a card or data carrier that can be inserted into the mobile terminal. For example, the transponder unit can be integrated into a SIM card. This has the advantage that the mobile terminal, for example a mobile phone or a PDA, into which the card is inserted with the transponder unit, according to the invention, does not require any additional (integrated) antenna to be able to be used as RFID unit.

Other characteristics and advantages of the invention emerge from the following description of exemplary embodiments, according to the invention, with reference to the accompanying drawings. In the drawings:

Figure 1 shows a system comprising a transponder unit and a reader apparatus;

Figure 2 schematically shows a transponder unit with a circuit, according to the invention; Figure 3 shows a basic connection diagram of an analog ring modulator;

Figure 4 shows an embodiment of an emitter for a ring modulator transponder unit;

Figure 5 shows an emitter for a transponder unit with ASK modulator as a carrier frequency modulator;

Figure 6 shows an emitter for a transponder unit with ASK modulator as a carrier frequency modulator and a modified subcarrier modulator;

Figure 7 shows a transponder unit in which, via an S2C interface, a security module has been attached to an interface component;

Figure 8 shows an interface component for a transponder unit, according to Figure 7;

Figure 9 shows a transponder unit in which, in another embodiment, a chip with a conventional HF interface has been attached to an interface component;

Figure 10 shows a transponder unit in which a chip with a conventional HF interface has been attached to a modified interface component; and

Figure 11 shows a part of a transponder unit in which a chip with a conventional HF interface has been inductively coupled to an interface component.

Figure 1 shows a system for data transmission comprising a transponder unit -1- and a reader apparatus -100- operating together with the transponder unit -1-.

The traditional reader device -100- can exchange data with passive transponders -200- traditional within the energy range -ER- and with active transponders -300- traditional within the communication range -KR-.

Depending on the type of system used, the data can be transmitted by the transponders -200-, -300- to the reader device -100- by means of load modulation (inductive coupling).

For data transmission, the transponder unit -1- sends to the reader device -100- a signal that the reader device -100- can recognize as a signal from a transponder, which performs a load modulation of the field -110- of the device. reader -100-. In contrast to the traditional -200-, -300- transponders, which modulate the field -110- of the reader device -100- to a field of the reader device -102-, -103-, the transponder unit -1-generates and emits its own modulated field -20- as a signal for data transmission. Thus, the transponder unit -1- uses its own energy for data transmission.

In order to achieve a better signal-to-noise ratio in an inductive system with a carrier frequency fT of the RFID reader of, for example, 13.56 MHz, a subcarrier fH is used in the known way where fH <fT, that is, for example, fH = 212 kHz. The load resistor is switched on and off in the transponder unit with the frequency fH, so that in the signal spectrum, together with the strong signal of the carrier frequency fT of the reading device, two subcarrier signals are generated with a separation of / - fH. When the subcarrier is modulated in the transponder unit -1-, according to the data to be transmitted, the modulation sidebands that carry the information are formed, located respectively below and above the two subcarriers. Thus, the data to be transmitted is contained in the same way in the sidebands of the subcarriers, arranged on the two sides of the two respective spectral lines. Data transmission is carried out by ASK, FSK or PSK modulation of the subcarrier, at the rate of the data flow. Contrary to subcarrierless load modulation, in which data is transmitted in sidebands located around the carrier frequency of the reader apparatus, the subcarrier signal can be better filtered and demodulated in the reader apparatus to recover the data.

Correspondingly, the transponder unit -1- generates and transmits a field -20-, comprising, at least, the modulation sidebands located around the carrier frequency fT or the modulation sidebands located around a subcarrier frequency fH , but which, as a general rule, comprises the modulation sidebands of the two subcarriers together with the two subcarriers.

Such a system can be used in a variety of ways and, in many applications, avoids the need for an additional interface in the reader apparatus.

For example, in a building where the system is installed as an access system, each person with access authorization can be authenticated by a transponder unit -1- made up of a chip card. The doors of the building equipped with the RFID readers of the access system, including the car entrances, can be opened by means of the chip card sufficiently in advance so that the automatic opening of the doors does not lead to waiting times.

Another example is the use in commercial establishments and storage or transport systems, in which the articles or containers for storage or transport are provided with a transponder unit, according to the invention. In this way, it is possible to register the articles or packages without major limitations of scope, in particular, also automatically.

On the other hand, a mobile terminal consisting of a transponder unit, according to the invention, could be used as a maintenance or surveillance unit, to check the functionality or carry out remote maintenance of multiple RFID readers, for example, in the checkouts from a supermarket or in an access system.

Figure 2 shows very schematically the transponder unit -1- in the form of an inductive coupling chip card, comprising the usual components not explicitly represented. To simplify the drawing, an RFID transponder unit according to the invention is shown on a chip card. The transponder unit has a battery -2-, an inductive antenna -3- and an electronic circuit -4-, -5-, -6-, -7-. The electronic circuit basically consists of three functional blocks, a receiver -4-, a control module -5- and an emitter -6-. A switch -7- serves to switch the antenna between the receiver -4- and the transmitter -6-. The receiver -4- has been provided to demodulate the signal transmitted by the reading apparatus -100-, in order to extract the data from it. The extracted data is redirected to the control module -5-, which processes them and generates the data to be transmitted to the reader -100-. Additionally, the control module -5- transmits a control signal to the switch -7-, which switches the transponder unit between the receive and transmit modes of operation. Instead, however, a separate antenna can be provided for the broadcast. As a control module -5-, for example, a part of the operating system of a portable data carrier, for example a chip card, can be used.

The emitter -6- consists of an oscillator -8-, a modulator for which an embodiment is initially described as ring modulator -9-, and a final amplifier -10-. Furthermore, the transmitter -6- of the transponder unit represented in figure 2 is complemented with an electronic component -11- designed to generate and modulate a subcarrier signal to carry out the transmission of data from the transponder unit to a reader device - 100- by means of a subcarrier signal. Depending on the application of the transponder unit, the subcarrier signal can have different frequencies, for example 848 kHz according to ISO 14443, 424 kHz according to ISO 15693 and 212 kHz for LEGIC, but it can also be completely omitted if applicable.

In the transponder unit shown in FIG. 2, it is provided that the component 11 divides the oscillator frequency by a predetermined factor by means of a frequency divider 12, for example with a binary division. The subcarrier signal thus generated is modulated with the data to be transmitted, which is supplied to the component -11- by the control module -5-.

Modulation of the subcarrier in component -11- is carried out, for example, in an AND gate by so-called 100% amplitude shift keying ("Amplitude Shift Keying", ASK). The amplitude of the signal generated by frequency division based on the data to be transmitted, is switched between the two states "on" and "off". As an alternative, a (B) PSK modulation can be carried out, for example according to ISO 14443 Type B, or an FSK modulation.

Both the oscillator signal and the ASK modulated signal generated in component -11- are conducted to the ring modulator -9-, the circuit configuration of which will be described in more detail with reference to Figure 3.

The ring modulator -9- has the peculiarity that it performs a special form of amplitude modulation. As in the usual amplitude modulation, on the sides of the oscillator frequency, the so-called carrier frequency, two spectral lines are generated which, observed in the frequency spectrum, are separated by the frequency of the ASK modulated signal. In the amplitude modulation in the ring modulator -9- the carrier frequency of the strong high-energy oscillator signal is largely suppressed. After the amplitude modulation in the annular modulator -9-, the data to be sent contained in the signal with ASK modulation is found in side bands around the two spectral lines of the subcarrier frequency. This kind of modulation is called double-side-band modulation ("Double-Side-Band", "DSB") or dual-band modulation with carrier suppression ("Double-Side-Band-Supressed-Carrier", "DSSC"). . No data is transmitted on the carrier frequency. On the other hand, with the use of the annular modulator -9- that suppresses the carrier frequency, the objective of being able to transmit data to the reader apparatus -100- is achieved with a lower emission power or with a notably greater range. The greater range is possible especially when the entire transmission power is used in the side bands where the data to be sent is located. Basically, the carrier frequency is necessary to demodulate the signal, in order to extract the data transmitted by the transponder unit in the reader apparatus. However, since the carrier frequency is still available in the reader apparatus, the transponder signal need not contain that frequency.

At the output of the ring modulator -9- there is then an output signal that contains the two modulation sidebands and that is (with sufficient precision) identical to a signal generated by load modulation or backscatter modulation. In your case, the output signal generated with the ring modulator -9- can be expanded by the amplifier -10- and driven by the switch -7-, which is switched to the transmission mode of the transponder unit by means of a signal from the control module -5-, to the antenna -3- for sending the data to be transmitted.

Direct connection of the annular modulator output with the antenna is also possible. However, in this case the antenna must be adapted appropriately and a possible impact on the annular modulator of the signal coupled by the reading device must be taken into account, since generally the same antenna is used for transmission and reception, and the device reader broadcasts continuously.

The transponder unit -1-, in a first (active) mode, functions as an active transponder / transmitter. In a second (passive) mode, on the other hand, the transponder unit works the same as an ordinary passive transponder, which carries out a charge modulation of the field of the reading device.

For example, the receiver -4- can be additionally configured as a traditional load modulator activated by the control module -5-. In this case, the control module -5- connects the emitter -6- and disconnects the load modulator, or it connects the load modulator and disconnects the emitter -6-. The switch 7 is toggled accordingly. As a criterion for switching the operating state from passive to active, for example, the magnitude of the received signal, the presence and / or sufficiency of an external voltage supply (on an optional "Vcc" connector, not shown) can serve. or the sufficiency of an internal voltage supply (battery charge status -2-). For example, a transponder unit -1- can be operated first in passive mode and then switched to active mode, for example, when the distance to the reading apparatus is unintentionally increased. The type of application for which the data is transmitted may also be a criterion for the mode of functioning. In safety critical applications, the transponder unit should only work in passive mode. On the other hand, a less critical application, for example, checking the right of access to spaces or buildings, will preferably work in active mode. The owner of the transponder unit should be able to select from time to time a default value of the general or preferred mode of operation, by means of a terminal apparatus in which the transponder unit is inserted or integrated. The switching between the active and passive modes of operation is preferably carried out while the transponder unit receives data, that is, in active or passive reception mode.

Figure 3 shows a basic connection diagram of an annular modulator -9-. As already described, the essential thing in the use of the annular modulator -9- is that it performs an amplitude modulation, so that, although the modulation sidebands of a subcarrier are generated in the usual way, it is suppressed in the greatest possible way. carrier frequency as possible. For example, in the transponder unit according to the invention, an MC1496 modulator ("Balanced Modulator") from the company "ON Semiconductor" can be used, which is especially suitable for carrier suppression. The ring modulator can be fully integrated into a transponder chip, so that a transponder chip, according to the invention, when all its components are fully integrated, only requires connections for the antenna -3- and the voltage supply. The input -HF- of the ring modulator -9- is fed with the high frequency output signal of the oscillator -8-. Preferably, the frequency of the oscillator signal is exactly the emission frequency of the reader device -100- (eg, 13.56 MHz). The input -NF- of the ring modulator -9- is fed with a baseband data signal (eg for the Felica system) or with a modulated subcarrier (eg for ISO 14443, ISO 15693) , as described above.

In the annular modulator -9- there are four diodes -14- connected forming a ring, so that each anode is connected to a cathode of the next diode -14-. One corner of the diode bridge is grounded and the signal at the input -NF- is coupled with a capacitor to the opposite corner. To achieve good carrier suppression, the oscillator signal is coupled from the -HF- input over a resistor bridge.

The baseband signal or modulated subcarrier signal introduced in the annular modulator -9- through the -NF- input, is switched at the rate of oscillation of the oscillator signal, between the normal form and the inverted form, with which the Symmetric voltages in opposition suppress the carrier frequency. The circuit depicted in Figure 3 is also called a balanced modulator.

Figure 4 schematically shows an alternative configuration of the emitter of a transponder unit with a digital ring modulator.

Without changes with respect to the configuration of figure 2, the binary data signal -A- is linked to a subcarrier signal -B- by means of an AND gate -43-. The linked signal is in contact with a ring modulator -49-. As ring modulator -49- an XOR element can be used. Unlike the configuration of the emitter of figure 2, a carrier signal -C- is not applied directly to the input of the ring modulator -49-. On the contrary, the carrier signal -C- is first linked in an AND gate -46- to a data signal -A-. This setting produces better performance, as explained in more detail later. The output signal of the ring modulator -49- is amplified in an amplifier -40-, before being emitted by the antenna -3- as a field of the transponder unit. By way of example, the signal types -A- to -C- are described in more detail below, with reference to Figure 5.

Figure 5 schematically shows an alternative emitter of a transponder unit without ring modulator. The emitter is used to generate an amplitude modulated signal, and the emitter shown is preferably used for binary data signals -A-, thereby creating an OOK ("on-off-keying") signal or a 2-ASK signal. The data signal -A- in the baseband (e.g. an NRZ signal or Manchester signal), a subcarrier signal -B- (e.g. 848 kHz for ISO / IEC 14443) and a carrier signal -C- (e.g. 13.56 MHz for ISO / IEC 14443) are ANDed using logic circuits -53- and -59-, so signals -A- are first ANDed. and -B- by means of the circuit -53-, with which the signal -E- is generated. Signal -E- is then ANDed with signal -C- by circuit -59-, thereby generating signal -D-. From the functional point of view, the circuit -59- adopts the function of the modulator and the circuit -53- takes on the role of the A ^nd gate -13- of figure 2.

In this case, the signal -D- emitted by an antenna -3- towards a reading device has a frequency spectrum equivalent to a frequency spectrum created by load modulation. In your case, the signal -D- can be amplified with an amplifier -40-. For example, the amplifier -40- can be a symmetric amplifier with output amplifiers of the "Push-Pull" type (push-pull).

Figure 6 shows schematically a small variation of the emitter of Figure 5.

In the emitter according to FIG. 5 an amplitude modulated subcarrier signal is generated, while the emitter that shown in FIG. 6 generates a phase modulated subcarrier signal. This transmitter, like the transmitter of FIG. 5, is used in a transponder unit, according to the invention, preferably only when the data signal -A- is a binary signal. Correspondingly, the emitter shown generates a BPSK signal ("2-PSK, Binary Phase Shift Keying"). In this case, a subcarrier signal -B- (eg 848 kHz for ISO / IEC 14443) and a carrier signal -C- (eg 13.56 MHz for ISO / IEC 14443) are ANDed together. , through the circuit -69-. The data signal -A- in the baseband (eg NRZ or Manchester signal), by means of a switch -63- and an inverter -64-, switches the subcarrier signal -B- between an inverted state and a not inverted state. The effect of this is equivalent to that of 180 ° phase modulation (BPSK, binary phase manipulation).

A signal -D-, which is created by a simple AND linkage of the subcarrier signal -E- modulated in phase with the carrier signal -C- and emitted by the antenna -3-, advantageously presents an equivalent frequency spectrum that of a load modulation with a subcarrier with BPSK modulation.

The following table shows an overview of the logical linkages of the signals, the power consumption and the range of different digital modulation switches (carrier frequency TF = 13.56 MHz, subcarrier frequency HT = 868 kHz and modulation signal MS in the baseband, Manchester 106 kBit / s).

A subcarrier with ASK modulation ("OOK, on-off-keying": HT n MS) according to ISO / IEC 14443-3 / Type A with a bit rate of 106 kBit / s initialization. If this signal is actively simulated according to the method according to the invention, the necessary sidebands can be most effectively generated with a ring modulator. The double sideband modulation (DSB) thus created should present the best results in terms of the range of communications, since the carrier frequency (13.56 MHz) is thereby suppressed and the available energy is provided to the bands. sides.

If an XOR element were simply used as a digital annular modulator with the circuit configuration of figure 2, in the studied signal, according to ISO / IEC 14443 - Type A, a bad suppression of the carrier would be obtained. This is mainly due to the fact that the carrier signal is also emitted during modulation pauses, that is, 100% of the time, and has an unnecessarily high power consumption.

When using a subcarrier with ASK modulation (OOK, for example, 14443 / Type A), in any case it is convenient to link the carrier frequency signal -TF-, intended to feed the digital annular modulator, with the signal of the baseband -MS- by means of a logical AND linkage (TF n MS) and use the resulting signal to feed an input of the digital annular modulator. With this, it is possible to reduce current consumption by 50%, if compared to the simple ring modulator. The HF signal is then emitted only at times when the subcarrier is also connected. The communication range of this circuit is exactly the same as the range of the single digital ring modulator. The carrier frequency is now clearly suppressed in the output spectrum, as expected from a ring modulator. With reference to FIG. 4, a circuit configuration of this kind has already been described.

The ASK modulator, as shown in Figure 4, is realized by AND linking all the input signals. The output signal now only consists of the carrier frequency pulses in rhythm with the subcarrier frequency and the modulation signal in the baseband. When it comes to range, you have to accept losses, and range is reduced to 83% of the range of the annular modulator. In contrast, the current consumption is only 25% of the consumption of the simple ring modulator. Thus, this modulation circuit appears to be especially advantageous, since the power consumption of the circuit, with a small reduction in range, can be reduced to 25%.

For an HF interface, for example with the S2C interface which is described in more detail below, an ASK modulator should preferably be used, since in this way the power consumption is minimal. When the HF interface is integrated into a smart card chip, or if an HF interface is used that makes the signal available (TF n MS), when there is sufficient power, the optimized ring modulator is preferably used. On the other hand, when energy needs to be saved, the ASK modulator can also be used in this case.

When data is transmitted from a transponder to a reader according to ISO / IEC 14443-3 / Type B, as well as with a baud rate of 212 kBit / s and higher, a subcarrier with BPSK modulation ("Binary Phase Shift Keying").

Also in the active reproduction of a signal of this kind, a ring modulator produces the best results with regard to the communication range. The digital ring modulator performs well when it comes to carrier suppression. However, the relative current draw is 100%, since HF energy is emitted for the entire duration of a bit.

The ASK modulator has an unfavorable response when it comes to carrier suppression. The current consumption, compared to the digital ring modulator, is reduced by 50%.

For subcarriers with BPSK modulation, or also FSK, an ASK modulator is preferably used, since in this case the emitter has a minimal current consumption. However, when sufficient power is available, the digital ring modulator can be used. An optimized digital ring modulator cannot be used, since with a PSK or FSK modulation of the subcarrier, it must be emitted for the entire duration of a bit. In the following, with reference to FIGS. 7 to 11, the advantageous possibilities of realization of a circuit according to the invention are set out in relation to known components.

There are smart card chips comprising the so-called S2C interface defined by the Philips company, to connect the smart card chip with an HF interface of an NFC device. These smart card chips have hardware elements to generate and decode the signals (Miller code, Manchester code, 848 kHz subcarrier) that require an ISO / IEC 14443 interface. However, a chip of this class does not have a unit. own HF interface.

Figure 7 schematically shows a transponder unit, according to the invention, constituted by an interface module (interface unit) -71-, connected to an antenna -3-, and a chip -75- with a suitable interface, for example , an S2C interface. A transponder unit of this kind can be realized, for example, in a mobile phone, with the SIM card as chip -75-, which is preferably connected to the interface module -71- via one or more contact surfaces. free (-C6- and / or -C4-, -C8-) of the SIM card.

Both the interface module -71- and the chip -75- can obtain their supply voltage from the apparatus, in which they are preferably arranged reversibly. The interface module -71-, in a second operating mode, can act as an ordinary transponder and supply the chip with an operating voltage -Vcc_RF-.

Figure 8 schematically shows a more exact configuration of an interface module for a chip with an S2C interface.

The interface module -71- is equipped with a signal input -SIGIN- and a signal output -SIGOUT-, to direct signals from the antenna to the chip (not shown) and from the chip, which generates the modulated subcarrier signal, to the antenna. A signal -SIGOUT- consists of a 13.56 MHz TTL signal which, in its case, contains a modulation signal from a remote reading device.

The interface module -71- comprises an amplifier -80-, an AND gate -89-, an oscillator -88-, a frequency divider -82-, a signal former -84- and a switch -87-. For example, the amplifier -80- can be a symmetric amplifier with output amplifiers (digital) of the "Push-Pull" type (push-pull). In addition, the interface module has two antenna connectors -La - and -LB- and a serial capacity -81-. Additionally, the interface module -71- has connections -Vcc-in and -GND- for the power supply and a control input -CTRL- to switch the interface module, by means of the switch -87-, between the operation broadcasting and receiving operation.

The external modulation subcarrier signal is conducted via a suitable interface (eg Philips S2C interface) to the signal input -SIGIN- of the interface module -71-, where it is processed as described below. For example, the subcarrier signal is an 848kHz TTL signal, modulating ASK (ISO / IEC 14443 A, Manchester Code) or BPSK (ISO / IEC 14443 B, NRC Code).

When the interface module is in transmission mode, that is, when a wireless data transmission is made to an external reader device or an NFC device, at the signal input -SIGIN-, by means of the smart card chip, a modulated subcarrier signal is fed and optionally inverted in an inverter 86. The inverted signal -E- is linked in the AND gate -89-, as a carrier frequency modulator, with a carrier frequency signal of 13.56 MHz, and is conducted to the amplifier -80-.

The antenna -3- and the series capacity -81- form an oscillating circuit in series, which is connected to the outputs -LA'- and -LB'- of the amplifier -80-, so that the HF current, which in case of resonance it flows in the oscillating antenna circuit, it is only limited by the ohmic resistances of the lines and of the amplifier -80-. As a result, the maximum possible emission power of the interface module is achieved.

In addition, from the oscillator -88-, with the switch -87- in emission operation, through the output -SIGOUT-, a uniform cycle signal of 13.56 MHz can be conducted to the smart card chip, provided that such an (external) cycle signal is required for operation in order to maintain exact timing ("Timing"). As already described, this is necessary for communication according to ISO 14443 Type A.

In reception operation, by means of the switch -87- and output -SIGOUT-, a digitized reception signal taken from the antenna -1- can be fed to the smart card chip. In this case, the signal former -84- functions as an amplifier, to be able to pick up weak signals, and as a threshold circuit, to provide a digitized output signal at the output of the signal former. For example, a Schmitt trigger can be used as the threshold circuit, which emits an unequivocal high or low level, depending on whether a predetermined threshold value is exceeded or not reached.

The "Push-Pull" outputs of the output driver (see amplifier units in figure 5) are switched to GND through the control input of the symmetric amplifier -80-, so that with the antenna -3- and the capacitor -41 -A parallel oscillator circuit is generated. In receiving operation of the interface module, the amplifier 80 can be switched to a current saving mode in order to save energy.

Oscillator 88 generates the 13.56 MHz carrier frequency signal necessary for broadcast operation. In the event that the oscillator cannot be switched off in reception mode, if necessary, because its transient regime is too long, the oscillator is operated with the interface module in reception mode, preferably at a multiple "N" of the carrier frequency signal (eg 27.120 MHz) so as not to disturb the receive signal with crosstalk, which may be weak. In broadcast operation, the 13.56 MHz signal can then be generated by dividing the oscillator signal by "N" using an optional divider -82-.

The control signal input -CTRL- for a control signal is optional, since the control signal for switching the operating mode can also be derived from the input signal at the signal input -SIGIN-. For example, a monostable time element (Monoflop), from the input signal in -SIGIN-, can generate a control signal. There is only one active signal input when the chip wants to send data. A control signal is obtained at the output of the time element when the monostable time element is triggered on the first edge of the input signal. In particular, the time element should be made retriggerable and set so that it falls back to the initial state, for example after a time equal to 1 or 2 times the duration of a bit (at most the FGT, " Frame Guard Time ", (" Frame security time "). Thus, the control signal activates a receive operation again when data is no longer sent. Figure 9 schematically shows the configuration of an interface module for connection to a chip with a conventional HF interface.

The active transponder unit according to the invention has a receiving branch and a transmitting branch. The transmission branch consists of an antenna -3-, an input amplifier -91-, an automatic amplification regulator -92-, as well as an amplifier, which is preferably configured as a symmetric amplifier (V +, V-) . In addition, there is a transponder chip -CL- connected to the symmetrical amplifier through its antenna connectors.

The transponder chip -CL- is a conventional RFID chip, according to the state of the art. It is normally connected in its connectors to an antenna, for example, on a chip card. On the other hand, the transponder chip -CL- is configured in such a way that the data transmission is carried out from the transponder unit to a reader device by means of charge modulation. This almost always happens anyway in the usual RFID systems used with 13.56 MHz or also with 125 kHz (eg ISO / IEC 14443, ISO / IEC 15693, ISO / IEC 18000-3).

The transmission branch consists of a demodulation circuit -97-, a modulator circuit -9-, an oscillator -8- (for example, 13.56 MHz), a control module -95-, as well as a signal amplifier. emission -80- connected to antenna -3-. The demodulation circuit -98- may comprise, for example, a rectifier -96 and a threshold value switch -97-.

In receive mode, the magnetic field of a distant RFID reader induces a voltage in the antenna -3-. Together with the capacitor -81-, the antenna -3- forms a parallel oscillating circuit whose resonance frequency is approximately equal to the emission frequency of the reading apparatus ^r F ⁱ D. The voltage that thus appears in the oscillating circuit it is driven to the input amplifier -91- by means of the switch -7-. By means of an amplification regulator -92- the amplification factor of the input amplifier -91- is monitored, so that the output amplitude of the voltage amplified by the input amplifier -91- remains largely constant. The time constant of the regulation is preferably adjusted in such a way that, although the output voltage of the amplifier -91- is kept constant for different distances from the reading device (that is, with voltages of different values in the coil - 3-), the modulation signals (eg 10% ASK with 106 kBit / s), on the other hand, are not suppressed due to too fast regulation.

The output signal of the amplifier -91- is conducted to another amplifier, preferably a symmetric amplifier (V +, V-). The output signal of the symmetric amplifier is conducted to the connections of the wireless RFID chip -CL- by at least one series resistor -93-. The amplitude of the output signal of the symmetric amplifier V + / V- is selected in such a way that the RFID chip -CL- can be supplied with sufficient energy through the output signal for its operation.

Thus, the RFID chip -CL- receives a signal that corresponds over time to the signal of the remote reading device and that behaves proportionally to it in terms of amplitude. With this, the RFID chip is also in a position to receive the instructions sent by said reading device, evaluate them and, where appropriate, process them.

As soon as the RFID chip -CL- has received and processed an instruction, it will try to send a response to the remote reader. For this, the RFID chip usually uses a load modulation, that is, an additional resistor in parallel of the chip is connected and disconnected with the passage of the modulation signal. This leads to measurable fluctuations in the voltage drop across resistors -93-, -94-. In other words, the amplitude of the alternating voltage HF is modulated in the connections. This amplitude modulated alternating voltage signal is demodulated by demodulation circuit -98-, so that the original modulation signal is reconstructed. The demodulation circuit -98-, in the simplest case, consists of a bridge rectifier -96- and a threshold value switch -97-. Another possibility is to implement the demodulation circuit with an A / D converter and further data processing (eg a DSP processor with software). In RFID systems that work with load modulated subcarriers, it is also possible to filter a subcarrier band created with load modulation (upper subcarrier band 13.56 MHz fHT, lower subcarrier band -13.56 Mhz - fm-) and further processing.

The modulation signal reconstructed by demodulation circuit -97- is also conducted to a control module -95-. This control module switches the switch, according to the invention, with the first edge of the modulation signal, instantaneously if possible, to a transmission operating mode, so that the data generated by the RFID chip -CL- can be transmitted to the remote reading apparatus. To do this, first switch -7- of antenna -3- is switched to oscillator -8- (13.56 MHz). This is necessary to be able to continue feeding the RFID chip -CL- with an alternating voltage of the correct frequency. At the same time, the amplifier -80- is activated by the control module -95-.

The reconstructed modulation signal as well as the oscillator signal -8- are conducted to the modulator circuit -9-. The exact function of such a circuit has already been described in detail. The output signal of the modulator circuit -9- is conducted to the amplifier -80- and transmitted to the remote reading apparatus via the antenna -3-.

According to the invention, it is provided that when no modulation signal is conducted to the control module -95- for a defined time "t", said module will switch the switch, according to the invention, back to the receive operating mode. The time "t" is preferably set between the duration of one bit (ISO 14443-A: ~ 10 ps) and the "Frame Delay Time" (minimum time until the next signal from a reading device, ISO 14443-A: ~ 86 ps). The signal that reaches the control module -95- from the reception branch (-91-, -92-, V +, V-) plays an important role. When a reading device sends data by modulation of the amplitude of the emitted field (e.g. 150 / IEC 14443-A: 100% ASK, ISO / IEC 14443-B: 10% ASK), this modulation is also transmitted to the transponder chip -CL-. It is possible that the demodulation circuit -98- cannot distinguish between a modulation signal from a reading device and a load modulation of the RFID chip -CL-, since both are manifested in the connections of the RFID chip -CL- in amplitude modulation form of signal 1Hf.

However, a load modulation of the transponder chip -CL- is only recognized in the connections, whereas, on the contrary, a modulation signal of the reading device is already recognized in the reception branch (-91-, -92 -, V +, V-) of the circuit, according to the invention. For this reason, it has been envisaged to connect the circuit, according to the invention, to the emission mode only when a modulation signal (amplitude modulation) can be detected exclusively in the connections of the RFID chip -CL-, but not in the reception branch. , since only in this case it is a load modulation. In figure 9 this is shown with the signal that feeds the control element -95- from the reception branch (-91-, -92-, V +, V-).

A second possibility of differentiation is the evaluation of the modulation depth of the signal in the connections of the RFID chip. With load modulation, a modulation depth of less than 100% is achieved. In an experimental model, approximately 25% was determined, and the combinations of different resistors -93-, -94- with different RFID chips -CL- lead to other values. For this reason, it has been envisaged that the differentiation between the load modulation and the modulation of the reading apparatus is carried out by determining the modulation depth on the basis of predetermined threshold values. If the magnitude of a modulation signal is greater than a first high threshold, it is a signal from the reader. On the contrary, if the modulation signal is less than the first switching threshold and optionally greater than a second switching threshold, it will be recognized that it is a load modulation. The switching to the emission mode will be carried out when the modulation has been produced by a load modulation.

Figure 10 schematically shows the composition of a simplified interface module intended to be connected to a chip with a conventional HF interface. In this embodiment, a symmetric TTL driver -23-, -24-, -25- is used instead of a linear amplifier. A modulation detector -22- serves to recognize an amplitude modulation sent by the reading device, and during the modulation pulses of the reading device, which performs 100% ASK modulation, according to the invention, it switches the two outputs to a low level. -23-, -24- of the symmetric circuit. On the other hand, if the transponder chip -CL- and the reading device use a 10% ASK modulation for data transmission (e.g. according to ISO / IEC 14443-B), it is foreseen that the modulation detector - 22- cycle the modulation signals between two symmetrical circuits with different output signal levels. Another possibility of coupling the transponder chip -CL-, but which is not part of the invention, is a capacitive or inductive coupling. Figure 11 shows the relevant part of a simplified interface module for an inductive connection to a transponder.

For inductive coupling, the circuit has an additional antenna -29- which is brought to resonance with the working frequency (eg, 13.56 MHz) by means of a capacitor -26-. Adjacent to the antenna -29- is a transponder consisting of a transponder chip -CL- and an antenna -28-, so that the best possible magnetic coupling can be achieved between the antennas -28- and -29-. Also in this configuration a charge modulation of the transponder chip -CL- can be easily detected.

The inductively coupled interface module and the additional antenna linked to it (see reference symbol -3- in Figure 10) may be arranged in a terminal apparatus. With the aid of such a terminal device, the range of an ordinary transponder can be increased. For example, the owner of a mobile phone could establish a communication between his transponder and a reader device that is unfavorably located or that for other reasons cannot be easily accessed, by bringing the transponder closer to his mobile phone equipped with an inductively coupled interface module, according to the invention.

The following table shows the results of the range measurements performed:

As can be seen in the table, with the method according to the invention, high communication ranges are achieved also with very small antennas.

It has been found that small antennas, for example on a SIM card with its own antenna (approx. 15 x 25 mm2), with conventional load modulation, only achieve very short reading distances. Communication with a wireless reader device is often even impossible when the SIM card with antenna is placed, for example, inside a mobile phone. Not only does the range considerably increase when one of the transmitters, according to the invention, is incorporated into a mobile terminal device. One can also take advantage of the fact that mobile terminal devices such as mobile phones, PDAs, etc., have their own power supply (battery), which can also be used to power a circuit, according to the invention.

To enhance the readability of this description, not all the advantageous features and configurations have been set forth, discussed and combined for each embodiment. It is possible to combine partial aspects of each embodiment with each other, as can be seen from the examples described in the following paragraphs.

The individual functional components of the transponder unit, i.e. the antenna, the interface unit, the chip and possibly the power supply unit, can be arranged separately in various combinations or can be integrated into a unit. For example, a transponder unit, according to the invention, can be formed as a special configuration transponder on a chip card which, optionally, can have a battery. A portable data carrier, in particular a SIM card with a chip and an interface unit, in a mobile terminal device can be connected to an external voltage source and / or to an external antenna. The interface unit arranged in a terminal device can be connected to its own or external antenna, and communicate with a chip permanently located in the terminal device or temporarily arranged on the terminal device.

For example, with the aforementioned combinations of components, a suitable modulation circuit can be chosen for the particular application case. Theoretically, also the various kinds of subcarrier modulators and carrier frequency modulators can be combined in any desired way. Depending on the application, it is also possible to foresee the passive operating mode as well as the conditions for switching over.

Claims (3)

1. Chip card with transponder unit (1) intended to transmit data to a reader device (100), to which transponder data can be transmitted by modulation of a field of the reader device, characterized by means for sending a signal which is evaluable to the reader apparatus as modulation by a transponder in order to transmit the data to the reader apparatus in a first mode of operation by an oscillator (8) to generate an oscillator signal and because the oscillator (8 ) is coupled via a phase-locked loop / PLL circuit to the signal received from the reading apparatus (100) and serving as a reference signal for the oscillator (8) and a modulator (9, 53, 63, 64) that is configured to modulate the oscillator signal by the data to be sent and to generate the output signal therefrom. 2. Chip card according to claim 1, characterized by, at least one antenna (3) to transmit signals from and / or to the reading apparatus (100); a receiver (4) for demodulating a signal transmitted by the reading apparatus (100) in order to extract the data therefrom; and an electronic circuit prepared to process the extracted data and generate the data to be sent to the reading apparatus (100). Chip card according to one of claims 1 or 2, characterized in that it comprises a load modulator and a switching device prepared to switch between the load modulator and a circuit module, according to the magnitude of the voltage induced in the antenna (3), to generate the output signal.